The heart valve is composed of extremely thin and flexible lamellar tissue, and the valve is opened and closed along with the contraction and relaxation of the heart. The heart of a normal person beats about 100,000 times per day and the valve is opened and closed 100,000 times per day. Thus, the heart valve must remain flexible and tensile, and be able to bear the pressure of the heart and the washing of the blood over a long period of time during the lifespan of a person.
Cardiac valve disease is one of the most common heart diseases in China, and is mainly caused by valve damage from rheumatic fever. Coinciding with the aging population in recent years, valve degeneration (including calcification, myxoid degeneration and the like) and valve damage of metabolism disorder are increasing in China. In addition, congenital valve disease is also one of the most common types of congenital heart disease.
Fifty years have elapsed since Professor Albert START implanted the first artificial heart mechanical valve in the human body and Professor Alain CARPENTIER implanted the first artificial heart biological valve in the human body in the 1960s. Both of these valves and the research behind them have brought about a turning point of life for cardiac valve patients.
As for which is better, based on years of clinical application, we make such a comparison that the patient who has a mechanical heart valve implanted needs to take anticoagulant for the duration of his or her life. The anticoagulant has many adverse side effects, e.g., it is very likely to cause bleeding or thromboembolism. The biological valve, meanwhile, does not require taking anticoagulant. However, after the biological valve is implanted in the patient's body, the leaflet will undergo an early-mid-phase calcification, thereby resulting in valve stenosis or regurgitation. The calcification phenomenon is especially severe in the bodies of young and middle-aged patients.
For the above reason, in half a century after these two types of valves came into use, the scientists continued to explore new ways of improving and developing them. The early direction of research was mainly targeted at processing for preventing the calcification, and along with the development of the medical technology later, the research field is enlarged to the improvement of the valve structure.
Quite a lot of high risk cases related to cardiac valve diseases, e.g., patients suffering from severe valve regurgitation, aged patients not suitable for the surgical valve replacement operation, patients suffering from advanced tumor and valve regurgitation, and patients suffering from multiple organ dysfunction and valve diseases, need to be treated by a new invasive method with small trauma. Then, the invasive cardiac valve came under the motivation of the surgical cardiac valve replacement operation. In recent years, the percutaneous valve interventions, e.g., the percutaneous pulmonary valve stent replacement; the percutaneous aortic valve heart valve replacement; the percutaneous mitral valve repair and the percutaneous mitral valve encircling constriction, emerged as the times require; it has achieved success after the percutaneous valve interventions being successively applied to the human beings since 2000; the initial result shows that the methods are practicable; the validity and risk of the invasive treatment must be further evaluated and compared; and the invasive treatment is only applied to high risk patients who cannot tolerate the surgical operation. The valve implantation of the percutaneous intervention pulmonary valve; the percutaneous aortic valve heart valve replacement; the percutaneous mitral valve repair; the percutaneous mitral valve annuloplasty; and the percutaneous mitral valve encircling constriction are all practicable, and the representation is that the heart function is improved after the implantation.
The development of the invasive treatment within the past 10 years shows that all of the cases which can be treated by the medical department and the surgical department can be treated by intervention, and the cases which cannot be treated by surgical operations can also be treated by intervention. In this century, research related to invasive treatments for valve disease is accelerated; the percutaneous intervention cardiac valve implantation is developed from the experimental research stage to a research stage with a small scale clinical practice running parallel; and the intervention of the valve diseases may break the technical “bottleneck”, rapidly achieve a wide clinical application, and again become the focus of attention in the field of interventional cardiology.
The U.S. Pat. No. 6,454,799 describes a balloon-expanded invasive cardiac valve, in which a biological valve is fixed on a plastically deformable stent; the valve is fixed to the balloon by radially compressing the stent; a percutaneous implantation is performed; and the stent is made to expand to be fixed by pressurizing the balloon after reaching the aortic valve. Such a balloon-expanded biological valve has the following disadvantages and problems: during the process of the compression of the stent and the expansion of the balloon, the tissue structure of the leaflet of the biological valve will suffer great damage, which severely affects the service life of the cardiac valve after the implantation; the stent of the cardiac valve is decided by the diameter of the balloon, if the selected size is too small, the valve has the risk of looseness or displacement, whereby a secondary balloon expansion is the only choice, and if the selected size is too large, there is a risk of tearing the aortic annulus, which results in the occurrence of other complications; with respect to such a cardiac valve, the balloon cannot be reset once it is expanded, and it will endanger the patient's life on the spot under the circumstance where the valve is placed in an improper position; and once the cardiac valve is implanted, if a problem arises, the valve cannot be retrieved and can be only replaced by means of a surgical operation.
The patent publication PCT/US2006/018514 describes a self-expanded invasive cardiac valve, in which a biological valve is fixed on a self-expanded stent; the stent is placed in a catheter of a carrier; a percutaneous implantation is performed; the stent is released after reaching the aortic valve; and the valve is made to be fixed with the aortic annulus by the structure of the stent itself. Such a self-expanded biological valve has the following disadvantages and problems: the stent is too long, and the design of the opening is unideal, which is likely to affect the hemodynamics of the left and right coronary ostia and results in disorder of the heart function; the cardiac valve which is released improperly cannot be reset, which will endanger the patient's life; and once the cardiac valve is implanted, if a problem arises, the valve cannot be retrieved and can be only replaced by means of a surgical operation.
The Chinese patent CN2726561 describes an invasive artificial cardiac valve, in which a leaflet is sutured on a tubular stent which is expandable and compressible; it is matched with a correspondingly designed implantation and retrieval device; a percutaneous implantation and an invasive extraction are performed; and a valve replacement is performed. Such a cardiac valve has the following disadvantages and problems: the stent is woven by threads, during the processes of compression and expansion, the grid is likely to be deformed, and the radial support force is unstable; there are a number of barbs at the outer side of the stent, although serving the purpose of preventing the displacement, they have a comparatively large damage to the vessel wall, meanwhile after the endothelialization, the retrieval of the stent is likely to tear the vessel, and the expected retrieval object is difficult to achieve; the design of the stent considers the positions of the left and right coronary ostia, but only two to three openings are left, the effect on the left and right coronary blood flows cannot be eliminated, and the positioning can hardly be performed when the cardiac valve is released.
It has been difficult to make much progress in the exploration of all the current products that have been clinically applied in the structure field. The current biological cardiac valve cannot be reset once it is opened, and it will endanger the patient's life on the spot under the circumstance where it is placed in an improper position.